KR20100087093A - Polythienylenevinylene thermoelectric conversion material - Google Patents

Abstract

(여기서, R1 및 R2는 각각 독립적으로 수소 원자, 또는 알콕시 또는 알킬 기임)로 나타내어지는 단위를 포함하는 폴리티에닐렌비닐렌을 포함하는 열전 변환 재료를 포함하며, 열전 변환 재료는 도펀트로 도핑된다.The thermoelectric conversion element is represented by the following formula 1:

Wherein R1 and R2 are each independently a hydrogen atom or an alkoxy or alkyl group, and include a thermoelectric conversion material comprising polythienylenevinylene, wherein the thermoelectric conversion material is doped with a dopant.

Description

Polythienylenevinylene thermoelectric conversion material {POLYTHIENYLENEVINYLENE THERMOELECTRIC CONVERSION MATERIAL}

Cross Reference with Related Application

This application claims the benefit of Japanese Patent Application No. 2007-239357, filed and pending on September 14, 2007, the disclosure content of which is incorporated herein by reference in its entirety.

The present invention relates to an organic thermoelectric conversion element, a thermoelectric conversion element comprising a polythienylenevinylene thermoelectric conversion material, and a method of manufacturing a thermoelectric conversion material.

Thermoelectric elements such as thermoelectric generators or Peltier elements advantageously have high thermoelectric conversion efficiency, are durable and are produced efficiently at low cost. Materials such as BiTe, SiGe, PbTe and cobalt oxide have all been proposed and intensively studied as thermoelectric conversion materials made from inorganic materials. Some of these inorganic materials have been found to have practical properties. However, of these materials, some materials must be produced through complex processes, and some produce toxic or toxic byproducts.

Organic thermoelectric materials, such as electrically conductive polymers, are usually readily processed and generally safe. However, in general, their thermoelectric conversion properties are considered to be incompatible with inorganic materials. Polyaniline has been disclosed as an electrically conductive polymer that can be used as a thermoelectric material (Japanese Patent Laid-Open No. 2000-323758 and Japanese Patent Laid-Open No. 2001-326393). Japanese Patent Laid-Open No. 2002-100815 discloses polyaniline in which the molecular structure is extended when dissolved in an organic solvent. The substrate spin-coated with this solution forms a thin film of thermoelectric conversion material. However, considering this manufacturing method, the production of a practical amount will be complicated. Japanese Patent Laid-Open No. 2003-332638 discloses poly (3-alkylthiophene) as a thermoelectric conversion material. This reference discloses that Seebeck coefficient and electrical conductivity increase when the thermoelectric conversion material is doped with iodine, resulting in improved thermoelectric conversion properties. Polyphenylenevinylene and alkoxy-substituted polyphenylenevinylene are disclosed in Japanese Patent Laid-Open No. 2003-332639 as a thermoelectric conversion material. Polyphenylenevinylene doped with sulfuric acid and alkoxy-substituted polyphenylenevinylene doped with iodine showed relatively good thermoelectric conversion properties. However, sulfuric acid-doped polyphenylene-vinylene is difficult to process and lacks stability in an air atmosphere.

Thus, there is still a need for organic thermoelectric conversion materials that have advantageous properties and can be easily manufactured.

Provided are an organic thermoelectric conversion element, a thermoelectric conversion element including a polythienylenevinylene thermoelectric conversion material, and a method of manufacturing a thermoelectric conversion material.

A thermoelectric conversion element is provided that includes a thermoelectric conversion material doped with a dopant. The thermoelectric conversion material includes polythienylenevinylene having thienylenevinylene units represented by the following general formula (1):

[Formula 1]

Wherein R ¹ and R ² are each independently a hydrogen atom, an alkoxy or an alkyl group.

Also provided is a method of making a thermoelectric conversion material. The method includes dissolving a polythienylenevinylene precursor in an organic solvent to form a precursor solution. The polythienylenevinylene precursor has two or more units represented by the following general formula (3):

 (3)

Wherein R ¹ and R ² are each independently a hydrogen atom or an alkoxy or alkyl group, and R ³ is an alkoxy group. The method comprises casting a precursor solution, drying the cast precursor solution to produce a precursor molded body, thermally decomposing the precursor molded body to prepare a polythienylenevinylene molded body, and a poly with doping material. And doping the thienylenevinylene molded body to produce a thermoelectric conversion material.

Unless otherwise indicated, all numbers expressing characteristic sizes, amounts, and physical characteristics used in the specification and claims are to be understood as being modified in all instances by the term "about." Accordingly, unless indicated to the contrary, the numerical parameters set forth in the foregoing specification and the appended claims may vary depending upon the desired properties sought to be achieved by one of ordinary skill in the art using the teachings disclosed herein. It is an approximation.

Reference to a numerical range by endpoint refers to any number within the range (eg, 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, and 5) and within that range. It includes any range.

As used in this specification and the appended claims, the singular forms "a", "an" and "the" include plural referents unless the content clearly dictates otherwise. As used in this specification and the appended claims, the term “or” is generally employed in its sense including “and / or” unless the content clearly dictates otherwise.

Disclosed herein is a thermoelectric conversion element comprising a thermoelectric conversion material and a method of manufacturing the material. In one aspect, a thermoelectric conversion element is provided that includes a thermoelectric conversion material. The thermoelectric conversion material includes polythienylenevinylene including a plurality of thienylenevinylenes which can be represented by the following general formula (1):

[Formula 1]

Wherein R ¹ and R ² are each independently a hydrogen atom, an alkoxy or an alkyl group. Polythienylenevinylene is doped with a dopant. In another embodiment, the thermoelectric conversion material may also include phenylenevinylene units, which may be represented by Formula 2:

[Formula 2]

In another aspect, a method of making a thermoelectric conversion material is provided. The method includes dissolving a polythienylenevinylene precursor in an organic solvent to form a precursor solution. The polythienylenevinylene precursor has repeating units that can be represented by Formula 3:

(3)

Wherein R ¹ and R ² are each independently a hydrogen atom, an alkoxy or an alkyl group, and R ³ is an alkoxy group. The method comprises casting a precursor solution, drying the cast precursor solution to produce a precursor molded article, thermally decomposing the precursor molded article to prepare a polythienylenevinylene molded article, and polythienylenevinyl as a doping material. And doping the len molded article to produce a thermoelectric conversion material.

Thermoelectric conversion elements disclosed herein include polymeric thermoelectric conversion materials made from flexible precursors. The flexible precursor is thermally decomposed to provide a thermoelectric conversion material having thermoelectric properties. The methods disclosed herein can provide thermoelectric conversion materials that can be used in the thermoelectric conversion elements disclosed herein.

Thermoelectric conversion materials disclosed herein include polythienylenevinylene comprising thienylenevinylene units represented by Formula 1 below:

[Formula 1]

Wherein R ¹ and R ² are each independently a hydrogen atom or an alkoxy or alkyl group. In one embodiment, the polymer comprising the repeating unit may be used as polythienylenevinylene. In one embodiment, the precursor can be used to form polythienylenevinylene. Exemplary precursors may be represented by the following formula (3).

(3)

In one embodiment, the polythienylenevinylene may be a copolymer that also includes phenylenevinylene units, which may be represented by Formula 2:

[Formula 2]

In one embodiment, comonomers comprising units of Formula 1 and Formula 2 may increase the processability of the precursor polymer.

In Formula 1 and Formula 3, R ¹ and R ² are each independently a hydrogen atom or an alkoxy or alkyl group. In one embodiment, R ¹ and R ² are each hydrogen atoms. Such embodiments may provide advantageous electrical conductivity properties. In one embodiment, R ¹ and R ² are each independently alkoxy or alkyl groups. In one embodiment, each of R ¹ and R ² is a lower alkoxy or lower alkyl group having up to 3 carbon atoms, eg, methyl, ethyl, n-propyl or isopropyl groups. In one embodiment, R ³ is an alkoxy group. In one embodiment where R ³ is an alkoxy group, its specific identity can be determined by the alcohol used as solvent during the preparation of the precursor polymer, as described below. For example, R ³ can be a methoxy group when methanol is used as solvent and R ³ can be an ethoxy group when ethanol is used as solvent.

In one embodiment, the polythienylenevinylene used in the present invention can be prepared by methods known to those skilled in the art. One such exemplary method can be found in the Journal of Chemical Society, Communication, 1448 (1987).

Particular exemplary methods of making polythienylenevinylene follow. The solution is prepared by dissolving 2,5-dimethylbis (tetrahydrothiophenium chloride) in a suitable solvent such as a methanol / water mixture. In one embodiment where thienylenevinylene and phenylenevinylene are copolymerized, p-xylenebis- (tetrahydrothiophenium chloride) may be added to this solution. The monomer solution is then cooled to low temperature (eg, about −30 ° C.) and stirred. Subsequently, a base such as sodium hydroxide or tetramethylammonium hydroxide is added in an amount approximately equivalent to that of the monomer and the resulting solution is further stirred at low temperature to affect the polymerization reaction. An acid, such as hydrochloric acid, is added dropwise to the reaction solution to stop the polymerization and allow the solution temperature to return to room temperature. The precursor polymer will precipitate out of solution. In certain examples disclosed above, the precursor polymer has the formula as shown in Formula 4:

[Formula 4]

In Formula 4, Me is a methyl group derived from a methanol solvent. Thus, this group can be modified by using other solvents such as other alcohols. The precursor polymer can be recovered and dried to provide a solid precursor polymer.

The solid precursor polymer is then dissolved in a suitable solvent such as N-methylpyrrolidone. The resulting solution is cast and dried to form precursor shaped bodies (eg films). Since the precursor molded body is flexible, the molded body can be easily processed (for example, cut or the like) according to the desired use.

The precursor molded body is then thermally decomposed by heating to a high temperature for several hours in an inert atmosphere such as a nitrogen atmosphere to produce polythienylenevinylene. In one embodiment, thermal decomposition may be performed at about 200 ° C. In one embodiment, pyrolysis can be carried out at temperatures below 120 ° C., for example by using an acid catalyst such as HCl gas. In such embodiments, lower pyrolysis temperatures can inhibit the formation of carbonyl groups that can lower electrical conductivity. In other embodiments, protic acids such as hydrochloric acid, acetic acid or formic acid can be used as the acid catalyst.

The precursor polymer film may optionally be stretched before thermal decomposition. This is not necessary but leads to an improvement in the output coefficient P of the thermoelectric conversion material (as defined below). Stretching can be carried out, for example, at a draw ratio of about 1.5 to about 10 (film length L ₁ after stretching / film length L ₀ before stretching). In embodiments in which the polymer precursor is stretched prior to thermal decomposition, the weight average molecular weight of the precursor polymer may be at least about 3 × 10 ⁴ . In embodiments in which the polymer precursor is stretched prior to thermal decomposition, the weight average molecular weight of the precursor polymer may be at least about 6 × 10 ⁴ . Such molecular weight can further improve the output coefficient P due to stretching because of the improvement in molecular orientation.

The resulting polymer can then be doped with a dopant to produce a thermoelectric conversion material. Examples of dopants that may be used include, but are not limited to, halogens such as iodine, Lewis acids such as PF ₅ , and halides such as FeCl ₃ . The dopant may be added in an amount of at least about 0.5 mole dopant per mole of repeating unit.

Any molecular weight polythienylenevinylene may be used. In one embodiment, the molecular weight of polythienylenevinylene may be about 10,000 to about 1,000,000. The molecular weight may generally correspond to the degree of polymerization of the polythienylenevinylene homopolymer of about 8 to about 800. If the degree of polymerization is too low, the material does not have sufficient strength. If the degree of polymerization is too high, the precursor polymer material can be difficult to process.

In embodiments in which the film is selectively stretched before thermally decomposing, a degree of polymerization of at least about 50 can improve molecular orientation, which can also improve thermoelectric properties. In other embodiments in which the film is stretched, a degree of polymerization of at least about 100 can improve molecular orientation, which can also improve thermoelectric properties.

The molecular weight of polythienylenevinylene can be measured by gel permeation chromatography (GPC) using polystyrene standards. Further details of certain exemplary measurement methods are described in the Examples.

The thermoelectric conversion properties of the thermoelectric conversion material can be evaluated by the output coefficient P. The output coefficient P can be determined by the electrical conductivity σ (S / cm) of the material and the electromotive force per temperature of the material, ie Seebeck coefficient S (V / K), which can be determined as follows:

P = S ² × σ (Wm ^-1 K ^-2 )

The polythienylenevinylene thermoelectric conversion material described herein may have an output coefficient P of at least about 10 × 10 ⁻⁸ W m ⁻¹ K ⁻² . In some embodiments, the thermoelectric conversion materials described herein may have an output coefficient P of at least about 100 × 10 ⁻⁸ W m ⁻¹ K ⁻² .

Thermoelectric conversion elements disclosed herein generally comprise a base unit comprising a thermoelectric conversion material disclosed herein electrically and physically connected to a thermoelectric conversion semiconductor or metal. Exemplary thermoelectric semiconductors include materials such as bismuth selenide or aluminum-doped zinc oxide. Exemplary metals include materials such as platinum or palladium. The thermoelectric conversion material may be connected (electrically, physically or both) to the thermoelectric conversion semiconductor or metal by known methods. Exemplary connection methods include the use of conductive paste bonding, or coatings such as deposition or sputtering.

In some embodiments, a plurality of basic units may be connected in series to form a thermoelectric conversion element. In embodiments in which a temperature difference is formed between the connection points, the device may be a thermoelectric generator capable of producing thermoelectric power. In embodiments where current is applied through the device, the device may be a Peltier cooler capable of transferring heat between the connection points.

[Example]

The invention is described below with reference to examples, but the invention is not limited thereto in any way.

Example 1

Polythienylenevinylene (PTV) was synthesized by the following procedure. 5.28 g of 2,5-thienylene dimethylbis (tetrahydrothiophenium chloride) was dissolved in a mixture of 49.2 mL of methanol and 9.6 mL of water. This solution was then purged with nitrogen gas. The solution was cooled to -30 [deg.] C. while stirring and an aqueous solution containing NaOH (15 mL) was added dropwise to the purged solution in an amount equivalent to that of the monomers. The monomer concentration was 0.2 M and the volume ratio of methanol to water was 2: 1. The solution was further stirred at −30 ° C. for 2 hours under a nitrogen gas flow. The reaction was then terminated by neutralizing this solution with hydrochloric acid. The solution temperature was slowly returned to room temperature with stirring. The yellow precipitate was recovered and washed with water with suction filtration. The solid was dried to yield the precursor polymer in a yield of 26.1%.

The molecular weight of the PTV precursor polymer obtained above was determined by gel permeation chromatography (GPC). GPC crystals were performed by dissolving the precursor powder in N-methylpyrrolidone (NMP) to prepare a solution comprising 0.1 wt.% Of the PTV precursor polymer. The change in refractive index at room temperature was observed while using an NMP solution containing 10 mM NaBF ₄ as the eluent. As a result, the weight average molecular weight of the precursor polymer was found to be 3.0 × 10 ⁵ based on polystyrene, and the polydispersion was found to be 8.7. Thus, the degree of polymerization was 250.

PTV precursor polymer dissolved in NMP was cast into a vessel and dried under reduced pressure to produce a PTV precursor polymer film. The PTV precursor polymer film was then thermally decomposed at 200 ° C. under nitrogen gas flow for 5 hours. The PTV film was subjected to infrared absorption measurements, peak disappearance at 1,087 cm ⁻¹ derived from the methoxy group of the precursor polymer was confirmed after thermal decomposition, and trans-vinylene CH length vibration peak at 919 cm ⁻¹ . peak) was observed. Therefore, formation of PTV was confirmed.

PTV film was doped with iodine to show electrical conductivity. PTV film was exposed to iodine vapor for doping. Specifically, the PTV film was placed in a container with solid iodo under reduced pressure at room temperature for more than 12 hours. After the doping treatment, the PTV film was completely doped with saturated iodine vapor. Doping time for complete doping was confirmed by measuring the electrical conductivity of the doped PTV film at various times. Typically, the doping time of 12 hours was long enough to completely dope the PTV film. The doping level was about two iodine atoms per repeat unit of PTV. The same doping procedure was used in all of the examples below. Two thermocouples (Pt / PtRh) were bonded (using carbon paste) to the surface of the film (center of film) and two electrodes (Pt) were bonded to both ends of the film to provide a measurement element. A temperature difference (about 5 K) was formed in the longitudinal direction of the sample using a heater. Subsequently, electromotive force and temperature difference were measured. The electromotive force per temperature difference, ie, Seebeck coefficient, was determined from the measured values. Four probes were used to measure electrical conductivity at the same time point. From the Seebeck coefficient S and the electrical conductivity σ, the output coefficient P was calculated using the following formula: P = S ² σ. The results are shown in Table 1.

Example 2

The PTV precursor polymer film obtained in Example 1 was stretched at an elongation ratio of two. The stretched film was thermally decomposed at 200 ° C. for 5 hours under a nitrogen gas flow to produce a PTV film. PTV film was doped with iodine using the procedure described in Example 1. The thermoelectric properties of the resulting PTV film were measured in the same manner as in Example 1. The results are shown in Table 1. The improvement of the thermoelectric properties by stretching can be seen by comparing the results of Example 1 and Example 2 in Table 1.

Example 3

PTV was synthesized as in Example 1 except for the following. 5.37 g of 2,5-thienylene dimethylbis (tetra-hydrothiophenium chloride) was dissolved in a mixture of 113 ml methanol and 23 ml water. The solution was cooled to −30 ° C. and with stirring, an aqueous solution (15 mL) containing 1.1 equivalents of NaOH (relative to monomer) was added dropwise to the solution. The monomer concentration was 0.1 M and the volume ratio of methanol to water was 3: 1. The solution was further stirred at −30 ° C. for 4 hours under a nitrogen gas flow. Further treatment of this solution occurred as in Example 1. The solid so obtained was dried to produce a precursor polymer in a yield of 17.6%.

The molecular weight of the PTV precursor polymer was determined by GPC. GPC crystals were performed as in Example 1, except that tetrahydrofuran (THF) was used instead of NMP. As a result, the weight average molecular weight of the precursor polymer was found to be 7.6 × 10 ⁴ based on polystyrene, and the polydispersity was found to be 4.4. Therefore, the degree of polymerization was 120.

The PTV precursor polymer film was cast in the same manner as in Example 1. This precursor polymer film was thermally decomposed at 200 ° C. for 10 hours under a nitrogen gas flow to produce a PTV film. The PTV film was doped with iodine using the same procedure described in Example 1. The thermoelectric properties of the resulting PTV film were measured in the same manner as in Example 1. The results are shown in Table 1.

Example 4

The PTV precursor polymer film obtained in Example 3 was stretched at an elongation of 2, which was thermally decomposed at 200 ° C. for 10 hours under a nitrogen gas flow to produce a PTV film. The PTV film was doped with iodine using the same procedure described in Example 1. The thermoelectric properties of the resulting PTV film were measured in the same manner as in Example 1. The results are shown in Table 1.

Example 5

The PTV precursor polymer film obtained in Example 3 was drawn at an elongation of 3, which was thermally decomposed at 200 ° C. for 10 hours under a nitrogen gas flow to produce a PTV film. The PTV film was doped with iodine using the same procedure described in Example 1. The thermoelectric properties of the resulting PTV film were measured in the same manner as in Example 1. The results are shown in Table 1. The improvement of the thermoelectric characteristic by extending | stretching can be seen by comparing the result of Example 3, Example 4, and Example 5.

Example 6

The PTV precursor polymer film obtained in Example 3 was thermally decomposed at 100 ° C. for 4 hours under a nitrogen gas flow containing a small amount of HCl gas to produce a PTV film. The PTV film was doped with iodine using the same procedure described in Example 1. The thermoelectric properties of the resulting PTV film were measured as in Example 1. The results are shown in Table 1. The improvement of the thermoelectric properties by thermal decomposition under other conditions can be seen by comparing the results of Examples 3 and 6.

Example 7

The PTV precursor polymer film obtained in Example 3 was stretched at an elongation of 2, which was thermally decomposed in the same manner as in Example 6 to produce a PTV film. The PTV film was doped with iodine using the same procedure described in Example 1. The thermoelectric properties of the resulting PTV film were measured in the same manner as in Example 1. The results are shown in Table 1. The improvement of the thermoelectric properties by stretching can be seen by comparing the results of Example 6 and Example 7.

Example 8

PTV was synthesized as in Example 1 except for the following. 5.88 g of 2,5-thienylene dimethylbis (tetrahydrothiophenium chloride) was dissolved in a mixture of 123 mL of methanol and 5 mL of water. The solution was cooled to -30 < 0 > C and with stirring, an aqueous solution (36 mL) containing 1.1 equivalents of NaOH (relative to monomer) was added dropwise to the solution. The monomer concentration was 0.1 M and the volume ratio of methanol to water was 3: 1. The solution was further stirred at −30 ° C. for 6 hours under nitrogen gas flow. Further treatment of this solution occurred as in Example 1. The solid was dried to yield the precursor polymer in a yield of 19.1%. The molecular weight of the PTV precursor polymer was determined by GPC as in Example 3. The increased average molecular weight of the precursor polymer was found to be 1.3 × 10 ⁴ based on polystyrene, and the polydispersity was found to be 2.7. Therefore, the degree of polymerization was 30. PTV precursor polymer film was obtained in the same manner as in Example 1. In addition, the polymer film was thermally decomposed in the same manner as in Example 5 to produce a PTV film. The PTV film was doped with iodine using the same procedure described in Example 1. The thermoelectric properties of the resulting PTV film were measured in the same manner as in Example 1. The results are shown in Table 1.

Example 9

The PTV precursor polymer film obtained in Example 8 was drawn at an elongation of 6, which was thermally decomposed in the same manner as in Example 6 to produce a PTV film. The PTV film was doped with iodine using the same procedure described in Example 1. The thermoelectric properties of the resulting PTV film were measured in the same manner as in Example 1. The results are shown in Table 1.

Comparison of the results from Examples 8 and 9 with other examples (for stretching of high molecular weight PTVs) indicates that the improvement of the thermoelectric properties of low molecular weight PTVs is less important even when the PTVs are drawn.

As such, embodiments of thermoelectric conversion materials are disclosed. Those skilled in the art will appreciate that the invention may be practiced in embodiments other than those disclosed. The disclosed embodiments are presented by way of illustration and not limitation, and the invention is limited only by the claims that follow.

Claims (10)

Formula 1:
[Formula 1]

Comprising a polythienylenevinylene comprising thienylenevinylene units represented by R ¹ and R ² , each independently being a hydrogen atom or an alkoxy or alkyl group, and comprising a thermoelectric conversion material doped with a dopant Thermoelectric conversion element. The thermoelectric conversion element of claim 1, wherein the thermoelectric conversion material has an output coefficient P of at least about 10 × 10 ⁻⁸ Wm ⁻¹ K ⁻² . 3. The thermoelectric conversion device of claim 1, wherein the polythienylenevinylene of the thermoelectric conversion material has a degree of polymerization of about 8 to about 800. 4. The thermoelectric conversion element according to claim 1, wherein the polythienylenevinylene of the thermoelectric conversion material is a stretched film having a degree of polymerization of at least about 50. 5. The thermoelectric conversion device according to any one of claims 1 to 4, wherein the polythienylenevinylene further comprises at least one phenylenevinylene unit represented by the following Chemical Formula 2:
(2)

. The thermoelectric conversion element according to claim 1, wherein the output coefficient P is at least about 100 × 10 ⁻⁸ W m ⁻¹ K ⁻² . Formula 3:
(3)

Wherein a polythienylenevinylene precursor comprising at least two units represented by R ¹ and R ² are each independently a hydrogen atom or an alkoxy or alkyl group and R ³ is an alkoxy group is dissolved in an organic solvent Preparing a precursor solution;
Casting the precursor solution;
Drying the cast precursor solution to prepare a precursor molded body;
Thermally decomposing the precursor molded article to prepare a polythienylenevinylene molded article; And
A method of manufacturing a thermoelectric conversion material, comprising the step of doping a polythienylenevinylene molded body with a doping material to produce a thermoelectric conversion material. The method of claim 7, wherein the thermal decomposition comprises heating to a temperature of less than about 120 ° C. in the presence of an acid catalyst. The method of manufacturing a thermoelectric conversion material according to claim 7 or 8, wherein the precursor molded body is a film, further comprising the step of stretching the film. The method of claim 9, wherein the precursor shaped body is a film and has a weight average molecular weight of at least about 3 × 10 ⁴ .